In recent years, in facing with an advanced information age, higher speed, higher integration and higher density packaging are demanded for semiconductor devices. In order to attain a higher speed in the semiconductor devices, in addition to shortening a wiring length and so on, it is indispensable to increase the signal propagation velocity on a circuit; in this connection, the signal propagation velocity is in inverse proportion to a square root of the dielectric constant of a substrate material; accordingly, a substrate material lower in the dielectric constant is necessary. Furthermore, in order to attain the higher integration and the higher density packaging, wiring materials low in the specific resistance (Ag, Au, Cu and so on) are demanded to use; however, since these metals are low in the melting point, in a multi-layered printed wiring board or the like in which after a wiring pattern is printed a substrate is sintered, it is necessary to use a substrate material capable of sintering at low temperatures. Accordingly, since alumina substrates (dielectric constant: from 9 to 9.5, sintering temperature: substantially 1500° C.) that have been so far widely used as a substrate material for use in electronic components are not suitable for high frequency printed circuit boards, in place of this, a material that is lower in the dielectric constant and capable of sintering at low temperatures is in demand. In addition, lower loss in microwave and millimeter wave regions is also in demand.
In this connection, recently, as a low dielectric constant substrate material capable of coping with higher speeds, a glass ceramic material made of glass and inorganic filler is under study. This kind of glass ceramic material, being such low in the dielectric constant as substantially from 3 to 7, is suitable for insulating substrates for use in high frequency, and in addition to the above, being capable of sintering at temperatures from 800 to 1000° C., is advantageously capable of sintering simultaneously with Ag, Au, Cu and so on low in the conductor resistance.
For instance, in JP-A-2000-188017 (U.S. Pat. No. 6,232,251), a ceramic composition for use in high frequency that includes a glass phase capable of precipitating a diopside (CaMgSi2O6) type crystal phase and an oxide containing Mg and/or Zn and Ti as the filler and is capable of sintering at a temperature equal to or less than 1000° C. is disclosed. Furthermore, in JP-A-2001-240470, a printed wiring board for use in high frequency that is made of a crystallized glass component containing SiO2, Al2O3, MO (M denotes an alkaline earth metal element) and Pb and a kind of filler selected from a group of Al2O3, SiO2, MgTiO3, (Mg, Zn)TiO3, TiO2, SrTiO3, MgAl2O4, ZnAl2O4, cordierite, mullite, enstatite, willemite, CaAl2Si2O3, SrAl2Si2O8, (Sr, Ca)Al2Si2O8 and forsterite is disclosed.
In addition, low temperature sintering ceramic compositions in which boron (B) is used as a sintering aide has been proposed (See JP-A-2002-037661, JP-A-2002-173367, etc.).
However, the conventional glass ceramic material, though low in the dielectric constant, is such high as 20×10−4 or more in the dielectric loss (tan δ) in a high frequency region of a signal frequency of 10 GHz or more, that is, substantially in the range of from 5×103 to 8×103 in terms of the Qf value; accordingly, it does not have the characteristics enough to put into practical use as the substrate material for high frequency. For example, the ceramic composition of JP-A-2000-037661 has a Qf value of at most 0.5×103 and the composition of JP-A-2002-173367 has a Qf value on the order of 5×103. The Qf value here denotes a product of a measurement frequency (f/GHz) and Q (≅1/tan δ).
Accordingly, the present invention intends to provide a low temperature sintering ceramic composition that can be sintered simultaneously with a low resistance metal such as Ag, Au, Cu or the like and realize low dielectric constant and the low dielectric loss in a high frequency region, and a fabricating method of the low temperature sintering ceramic.